Light signal



Oct. 11 1927.

LIGHT SIGNAL Find-Aug. 24, 1922 1,644,834 J. s. HoBsoN ATTORNEY Patented Oct. 11, l'9`2-7.

UNITED STATES 1,644,834 PATENT OFFICE.

JOHN S. HOBSON, OF CHICAGO, ILLINOIS,`ASSIGNOR TO THE SWITC & SIGNAL COMPANY, F SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

LIGHT SIGNAL.

Application led August 24, 19.22. Serial` No. 584,144.

My invention relates to light signals, and is particularly well adapted for signals of this type which are used in railway traiic controlling systems.

One-feature of my'invention is the protioned, one. form of signal embodying my invention. Fig. 2 isa sectional view on the line II-II of Fig. l.

Similar reference charactersirefer to similar parts in each of the views. A

Referring to the drawing, the signal comprises a casing 2provided with a rear door 2, which .casing contains 'three light units, P, C and S, indicating when lighted, proceed,"caution and stop, respectively.

Referring particularly to the stop unit S, it will be seen that this unit comprises an incandescent lamp f3, and a lens combination 4 for projecting a beam of light from this lamp toward atrain approaching the signal. The lamp 3, which I will term'the main lamp lof the unit, is so located that its filament is at the focus of the lens combination 4, so that the projection of light from this lamp is comparatively efiicient. The lens combination 4 includes a colored glass, usually red, which glass may be separatev from the lenses or'may be one of the lenses themselves, the result in leither instance being that the light projected from this unit toward a train approaching the signal is red. The light unit S also includes an auxiliary lamp 5, which is so located that its filament is a considerable distance behind the focus of the lens combination 4. The unit is provided with a refiector 6, the function of which is to project light from the auxiliary lamp 5 to the focal center of the lens combination 4 from which point such light is, of course, rejected in the ,same manner as the light irom the main lamp 3. The purpose of the auxiliary lamp 5 is to give a comparatively faint short-range indication in the event that the main lamp` 3 burns out.

The proceed unit P and the caution unit C, are the same as the stop unit S, consequently further explanation of these units is unnecessary, it being understood, of l course, that the light projected from each unit is different in color. Ordinarily, the light from the'proceed unit P will be green, and that from thecaution unit C will be yellow.

As is well understood in railway^ signal-v ing practice, the control of the signal is usually such that as a train passes the signal the stop unit S becomes lighted to indicate to a following train 'that the block protected by the signal is occupied. It is frequently desirable, however, that the engine driver should be able to determine that the stop funit S has become lighted, or that this fact should be apparent to others on the train which has passed the signal. For this ,rea-

son I have provided a ba'ck light for the stop unit S which I will now describe.

Located above the main lamp 3 is a frame 7 attached to the casing 2 and containing a condensing lens 8, which lens projects a beam of light from the lamp 3 upwardlyy and slightly to one side as will be apparent from Eig. 1. Located in the path of this beam is a mirror 9 attached to a suitable frame 10 mounted in the signal casing 2. which mirror delects the beam horizontally toward the back of the signal. This beam of light passes through a glass window 11 in the rear door 2*. which window is protected by a hood 12 to shield the window from outside light. The inner surface of thel glass window 11 is preferably sandblasted or ground in other suitable manner.

It will be seen from the foregoing that whenthe main lamp 3 of the stop unit S is lighted, an uncolored beam of light from this lamp is projected from the back of the signal, so thatit may be seen from a train lamp 5 is an auxiliary lamp only, and is provided to avoid interruption to traic if the main lamp 3 should burn out. When the auxiliary ,lamp 5 is lighted and the main lamp 3 is extinguished, the signal is not functioning in its normal manner, and so it is not. desirable at such time to, project Va beam of light through lthe window 11.

One feature of the specific structure shown in the present application is that any light from an outside source which may enter the rear window 11 and reach the mirror 9 will not be projected from the front of the signal through the .lens combination 4 of the stop unit S.

Although I have herein shown and described only one form of signal embodying my invention, it is understood that various chan es and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.'

-IIaving thus described my invention, what' I claimis:

1. A light signal comprising optical means -for projectin a beam lof light towards a train approac ing the signal, a main lamp located substantially at the focal point of said optical means, an auxiliary lamp located well out of the focal point of said optical means but in such position that light is projected therefrom by said means, an-d other` means for projecting a beam of light from said' mam lamp but not fromsaid auxiliary lamptowards a train leaving said signal.

'2. A light signal comprising optical means for. projectin a beam oflight towards .a tram ap roac in the signal, `a main lamp located su stantial y at the focal point of said olptical means, an auxiliary lamp located in t e rear of said focal point, a reflector located behind said auxiliary lamp for pro- ]ectmg light therefrom to said focal point, and means including a mirror for projecting a beam of light from said main lamp around saild r-eiector and out at the back ofthe signa v s 3. A light signal comprising optical means for projectin a beam of lightv towards a tram approac ing the signal, a main lamp located substantially at the focal point of said optical means, an auxiliary lamp located in the rearof said focal point, a re- Hector located behind said vauxiliary lamp for projectingv light therefrom to'v said focal oint, a condensing lens for .projecting a eam of light from said main lamp at sub- Astantially right angles to4 the axis of said optical means, and a mirror for directing said last-mentioned beam of light toward. an openin in the back of the si 4. "A lig t signal comprising) a amp, optical means for projecting a ea-m of light from said lamp out of the front of the signal,

a lens for projecting. an' additional beam of light from saidlamp at substantially right angles to the axis of said optical means, and a mirror for directing vsaid last-mentioned beam of light toward an opening in the back of the signal, the openingszin the front and back of said si al 'being non-registering, and the with the ront openingwbeing opaque so that light from the outside strikin the back of the signal cannot be projected rom the front.

the part of the back wall of said casing registering with" said front aperture being opaque so that light from the outside striking the back of the casing cannot be projected from the front aperture to cause the signal to falsely appear illuminated.

6. A railway light signal comprising a casing having two non-registering apertures in art o the back wall registering- Itowards a train receding from said signal,

the front and back respectively, a lens mounted 'in the front aperture, a light source located in said casing in the axial line of said lens, and means for projecting through said back aperture a beam made up of rays/from said source which could not be utilized byV said lens, the part of the back' wall of said casing registering with said front aperture being opaque so that light from the outside striking the back of the casing cannot be projected from the front aperture to cause the signal to falsely appear illuminated.

7 A railway light signal comprising a ca sing, having two non-registering openings 1n 05 the front and back respectively, a light source located in said casing in the axial line k'of saidfront aperture, a lens mounted in said front aperture for receiving a conical beam frontsaid source and transmitting'it as a beam of parallel rays towards a train approaching said signal, and means for projecting through said back aperture 'a beam made` up of rays from said source not included in the conical beam received by said lens, the part of the back wall of said casing registering with said frontaperture bein opaque l so that light from the outside stri ing the Iback of the casing cannot be projected from theffront aperture to causev the signal to Afalsely appear illuminated. v

In testlmony whereof I affix my signature.

JOHN S. HOBSON. 

